Planetary gear train of automatic transmission for vehicles

ABSTRACT

A planetary gear train of an automatic transmission may include a first planetary gear set outputting a negative rotation speed by using a rotation speed selectively input from the input shaft, a second planetary gear set outputting a reduced rotation speed by using the rotation speed selectively input from the input shaft or to selectively become a direct-coupling state together with the first planetary gear set, a compound planetary gear set having four rotation elements by combining third and fourth planetary gear sets, seven rotational members including two rotation elements connected to each other or one rotation element among the rotation elements of the first and second planetary gear sets and the compound planetary gear set, and six friction members including clutches, and brakes.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2011-0130513 filed in the Korean Intellectual Property Office on Dec.07, 2011, the entire contents of which is incorporated herein for allpurposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic transmission for vehicles.More particularly, the present invention relates to a planetary geartrain of an automatic transmission for vehicles which improves powerdelivery performance and reduces fuel consumption.

2. Description of Related Art

Typically, a planetary gear train is realized by combining a pluralityof planetary gear sets, and the planetary gear train including theplurality of planetary gear sets receives torque from a torque converterand changes and transmits the torque to an output shaft.

It is well known that when a transmission realizes a greater number ofshift speeds, speed ratios of the transmission can be more optimallydesigned, and therefore a vehicle can have economical fuel mileage andbetter performance. For that reason, the planetary gear train that isable to realize more shift speeds is under continuous investigation.

Though achieving the same number of speeds, the planetary gear train hasa different operating mechanism according to a connection betweenrotation elements (i.e., sun gear, planet carrier, and ring gear).

In addition, the planetary gear train has different features such adurability, power delivery efficiency, and size depend on the layoutthereof. Therefore, designs for a combining structure of a gear trainare also under continuous investigation.

In addition, the planetary gear train realizes a plurality ofshift-speeds. However, another friction member must be operated afterone friction member is released so as to shift to a neighboringshift-speed from a view of shift control.

In addition, a step ratio between the neighboring shift-speeds should becontrolled to be suitable according to the planetary gear train.

Currently, four-speed and five-speed automatic transmissions are mostoften found on the market. However, six-speed automatic transmissionshave also been realized for enhancement of performance of powertransmission and for enhanced fuel mileage of a vehicle. In addition,eight-speed automatic transmissions and tenth-speed automatictransmissions have been developed at a good pace.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing aplanetary gear train of an automatic transmission for vehicles havingadvantages of achieving nine forward speeds and a reverse speed withimproved controllability of friction members, suitable step ratios, andimproved performance and fuel economy by combining a plurality ofplanetary gear sets with a plurality of friction members.

In a planetary gear train of an automatic transmission for vehicles, mayinclude an input shaft adapted to receive engine torque, an output shaftadapted to output a shifted torque, a first planetary gear setoutputting a negative rotation speed by using a rotation speedselectively input from the input shaft, a second planetary gear setoutputting a reduced rotation speed by using the rotation speedselectively input from the input shaft or to selectively become adirect-coupling state together with the first planetary gear set, acompound planetary gear set having four rotation elements by combiningthe third and fourth planetary gear sets, and changing the rotationspeed selectively input from the input shaft through two paths and thenegative rotation speed and the reduced rotation speed inputrespectively from the first and second planetary gear sets into nineforward speeds and one reverse speed and to output the nine forwardspeeds and the one reverse speed, seven rotational members including tworotation elements connected to each other or one rotation element amongthe rotation elements of the first and second planetary gear sets andthe compound planetary gear set, and six friction members includingclutches interposed between a selected rotational member among the sevenrotational members and the input shaft or between selected rotationalmembers, and brakes interposed between a selected rotational memberamong the seven rotational members and a transmission housing.

In another aspect of the present invention, a planetary gear train of anautomatic transmission for vehicles achieving multiple shift-speeds mayinclude an input shaft adapted to receive engine torque, an output shaftadapted to output a shifted torque, a first planetary gear set being asingle pinion planetary gear set having a first sun gear, a first planetcarrier, and a first ring gear, a second planetary gear set being adouble pinion planetary gear set having a second sun gear, a secondplanet carrier, and a second ring gear, a compound planetary gear set ofRavingneaux type having a third sun gear, a fourth sun gear, a commonplanet carrier, and a common ring gear, a first rotational memberincluding the first sun gear and selectively connected to the inputshaft, a second rotational member including the first planet carrier andthe second sun gear, and directly connected to a transmission housing, athird rotational member including the first ring gear, the second ringgear, and the third sun gear, a fourth rotational member including thesecond planet carrier and selectively connected to the input shaft, afifth rotational member including the common planet carrier, andselectively connected to the input shaft or to the transmission housing,a sixth rotational member including the common ring gear and directlyconnected to the output shaft, a seventh rotational member including thefourth sun gear and selectively connected to the input shaft, and sixfriction members including clutches interposed between a selectedrotational member among the seven rotational members and the input shaftor between selected rotational members, and brakes interposed between aselected rotational member among the rotational members and thetransmission housing.

The compound planetary gear set of Ravingneaux type may include thecommon ring gear, the common planet carrier, the third sun gear engagedwith a long pinion, and the fourth sun gear engaged with a short pinionengaged with the long pinion, and the fourth sun gear is engaged to theshort pinion, wherein the common ring gear is engaged to the longpinion.

The long pinion may include a large-diameter portion and asmall-diameter portion, the third sun gear is engaged to thelarge-diameter portion, and the common ring gear and the short pinionare engaged to the small-diameter portion, wherein the common ring gearis engaged to the small-diameter portion.

The six friction members may include a first clutch interposed betweenthe input shaft and the first rotational member, a second clutchinterposed between the input shaft and the fourth rotational member, athird clutch interposed between the input shaft and the seventhrotational member, a fourth clutch interposed between the input shaftand the fifth rotational member, a fifth clutch interposed between thesecond rotational member and the fourth rotational member, and a firstbrake interposed between the fifth rotational member and thetransmission housing.

In further another aspect of the present invention, a planetary geartrain of an automatic transmission for vehicles achieving multipleshift-speeds, may include an input shaft adapted to receive enginetorque, an output shaft adapted to output a shifted torque, a firstplanetary gear set having a first sun gear, a first planet carrier, anda first ring gear, a second planetary gear set having a second sun gear,a second planet carrier, and a second ring gear, a compound planetarygear set formed by combining a third planetary gear set having a thirdsun gear, a third planet carrier, and a third ring gear and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear, a first rotational member including the firstsun gear and selectively connected to the input shaft, a secondrotational member including the first planet carrier and the second sungear, and directly connected to a transmission housing, a thirdrotational member including the first ring gear, the second ring gear,and the third sun gear, a fourth rotational member including the secondplanet carrier and selectively connected to the input shaft, a fifthrotational member including the third planet carrier and the fourth ringgear, and selectively connected to the input shaft or to thetransmission housing, a sixth rotational member including the third ringgear and the fourth planet carrier, and directly connected to the outputshaft, a seventh rotational member including the fourth sun gear andselectively connected to the input shaft, and six friction membersincluding clutches interposed between a selected rotational member amongthe seven rotational members and the input shaft or between selectedrotational members, and brakes interposed between a selected rotationalmember among the seven rotational members and the transmission housing.

The first planetary gear set is a single pinion planetary gear set, thesecond planetary gear set is a double pinion planetary gear set, thethird planetary gear set is a single pinion planetary gear set, and thefourth planetary gear set is a single pinion planetary gear set.

The six friction members may include a first clutch interposed betweenthe input shaft and the first rotational member, a second clutchinterposed between the input shaft and the fourth rotational member, athird clutch interposed between the input shaft and the seventhrotational member, a fourth clutch interposed between the input shaftand the fifth rotational member, a fifth clutch interposed between thesecond rotational member and the fourth rotational member, and a firstbrake interposed between the fifth rotational member and thetransmission housing.

The multiple shift-speeds may include a first forward speed achieved byoperating the first clutch and the first brake, a second forward speedachieved by operating the third clutch and the first brake, a thirdforward speed achieved by operating the first clutch and the thirdclutch, a fourth forward speed achieved by operating the third clutchand the fifth clutch, a fifth forward speed achieved by operating thesecond clutch and the third clutch, a sixth forward speed achieved byoperating the third clutch and the fourth clutch, a seventh forwardspeed achieved by operating the second clutch and the fourth clutch, aneighth forward speed achieved by operating the fourth clutch and thefifth clutch, a ninth forward speed achieved by operating the firstclutch and the fourth clutch, and a reverse speed achieved by operatingthe second clutch and the first brake.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a planetary gear train according to thevarious exemplary embodiments of the present invention.

FIG. 2 is a diagram showing connections of a planetary gear trainaccording to the various exemplary embodiments of the present invention.

FIG. 3 is an operational chart of friction members at each shift-speedapplied to a planetary gear train according to the various exemplaryembodiments of the present invention.

FIG. 4 is a schematic diagram of a planetary gear train according to thevarious exemplary embodiments of the present invention.

FIG. 5 is a schematic diagram of a planetary gear train according to thevarious exemplary embodiments of the present invention.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

An exemplary embodiment of the present invention will hereinafter bedescribed in detail with reference to the accompanying drawings.

Description of components that are not necessary for explaining thepresent exemplary embodiment will be omitted, and the same constituentelements are denoted by the same reference numerals in thisspecification.

In the detailed description, ordinal numbers are used for distinguishingconstituent elements having the same terms, and have no specificmeanings.

FIG. 1 is a schematic diagram of a planetary gear train according to thefirst exemplary embodiment of the present invention, and FIG. 2 is adiagram showing connections of a planetary gear train according to thefirst exemplary embodiment of the present invention.

Referring to FIG. 1 and FIG. 2, a planetary gear train according to thefirst exemplary embodiment of the present invention includes first,second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4disposed on the same axis, an input shaft IS, and output shaft OS, sevenrotational members TM1-TM7 directly or selectively connecting rotationelements of the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4, six friction members C1-C5 and B1, and atransmission housing H.

In addition, the first and second planetary gear sets PG1 and PG2 areoperated independently, and a compound planetary gear set CPG ofRavingneaux type is formed by combining the third and fourth planetarygear sets PG3 and PG4.

A rotation speed input from the input shaft IS is changed by the firstand second planetary gear sets PG1 and PG2 and the compound planetarygear set CPG and is output through the output shaft OS.

In addition, the planetary gear sets are disposed in a sequence of thefirst and second planetary gear sets PG1 and PG2 and the compoundplanetary gear set CPG from an engine to the rear.

The input shaft IS is an input member, and torque from a crankshaft ofthe engine is changed through a torque converter and is input to theinput shaft IS.

The output shaft OS is an output member and delivers driving torque soas to run driving wheels through a differential apparatus.

The first planetary gear set PG1 is a single pinion planetary gear set,and includes a first sun gear S1, a first ring gear R1, and a firstplanet carrier PC1 rotatably supporting a first pinion P1 engaged withthe first sun gear S1 and the first ring gear R1.

The second planetary gear set PG2 is a double pinion planetary gear set,and includes a second sun gear S2, a second ring gear R2, and a secondplanet carrier PC2 rotatably supporting a pair of second pinions P2engaged with the second sun gear S2 and the second ring gear R2.

The compound planetary gear set CPG is formed by combining the thirdplanetary gear set PG3 being a single pinion planetary gear set and thefourth planetary gear set PG4 being a double pinion planetary gear setso as to be the compound planetary gear set of Ravingneaux type having aring gear and a planet carrier in common.

Therefore, the compound planetary gear set CPG is operated by fourrotation elements including the ring gear, the planet carrier, and twosun gears. For convenience of explanation, the ring gear is called acommon ring gear R34, the planet carrier is called a common planetcarrier PC34, the sun gear engaged with a long pinion P3 is called athird sun gear S3, and the sun gear engaged with a short pinion P4 iscalled a fourth sun gear S4.

At least one of rotation elements of the first and second planetary gearsets PG1 and PG2 and the compound planetary gear set CPG is directlyconnected to each other.

In further detail, the first ring gear R1 of the first planetary gearset PG1 is directly connected to the second ring gear R2 of the secondplanetary gear set PG2 and the third sun gear S3 of the compoundplanetary gear set CPG, and the first planet carrier PC1 of the firstplanetary gear set PG1 is directly connected to the second sun gear S2of the second planetary gear set PG2.

Therefore, the planetary gear train according to the first exemplaryembodiment of the present invention includes seven rotational membersTM1-TM7.

The first rotational member TM 1 includes the first sun gear Si and isselectively connected to the input shaft IS so as to be operated as aselective input element.

The second rotational member TM2 includes the first planet carrier PC1and the second sun gear S2, and is directly connected to thetransmission housing H so as to be always operated as a fixed element.

The third rotational member TM3 includes the first ring gear R1, thesecond ring gear R2, and the third sun gear S3.

The fourth rotational member TM4 includes the second planet carrier PC2and is selectively connected to the input shaft IS so as to be operatedas a selective input element.

The fifth rotational member TM5 includes the common planet carrier PC34,and is selectively connected to the input shaft IS so as to be operatedas a selective input element or is selectively connected to thetransmission housing H so as to be operated as a selective fixedelement.

The sixth rotational member TM6 includes the common ring gear R34 and isdirectly connected to the output shaft OS so as to be operated as afinal output element.

The seventh rotational member TM7 includes the fourth sun gear S4 and isselectively connected to the input shaft IS so as to be operated as aselective input element.

In addition, rotational members operated as selective input elementsamong the rotational members TM1-TM7 are selectively connected to theinput shaft IS through clutches C1, C2, C3, and C4, and the rotationalmembers among the rotational members TM1-TM7 are connected to each otherthrough a clutch C5.

In addition, the rotational member operated as the selective fixedelement among the rotational members TM1-TM7 is connected to thetransmission housing H through a brake B1.

A first clutch C1 is interposed between the input shaft IS and the firstrotational member TM1 so as to operate the first rotational member TM1as the selective input element.

A second clutch C2 is interposed between the input shaft IS and thefourth rotational member TM4 so as to operate the fourth rotationalmember TM4 as the selective input element.

A third clutch C3 is interposed between the input shaft IS and theseventh rotational member TM7 so as to operate the seventh rotationalmember TM7 as the selective input element.

A fourth clutch C4 is interposed between the input shaft IS and thefifth rotational member TM5 so as to operate the fifth rotational memberTM5 as the selective input element.

A fifth clutch C5 is interposed between the second rotational member TM2and the fourth rotational member TM4 so as to cause the first and secondplanetary gear sets PG1 and PG2 to become direct-coupling states. Atthis time, the rotation elements of the first and second planetary gearsets PG1 and PG2 are operated as fixed elements.

A first brake B1 is interposed between the fifth rotational member TM5and the transmission housing H so as to operate the fifth rotationalmember TM5 as the selective fixed element.

Friction members including the first, second, third, fourth, and fifthclutches C1, C2, C3, C4, and C5 and the first brake B1 are conventionalmulti-plate friction elements of wet type that are operated by hydraulicpressure.

FIG. 3 is an operational chart of friction members at each shift-speedapplied to a planetary gear train according to the first exemplaryembodiment of the present invention.

As shown in FIG. 3, two friction members are operated at eachshift-speed to according the first exemplary embodiment of the presentinvention.

A first forward speed D1 is achieved by operating the first clutch C1and the first brake B1.

A second forward speed D2 is achieved by operating the third clutch C3and the first brake B 1.

A third forward speed D3 is achieved by operating the first clutch C1and the third clutch C3.

A fourth forward speed D4 is achieved by operating the third clutch C3and the fifth clutch C5.

A fifth forward speed D5 is achieved by operating the second clutch C2and the third clutch C3.

A sixth forward speed D6 is achieved by operating the third clutch C3and the fourth clutch C4.

A seventh forward speed D7 is achieved by operating the second clutch C2and the fourth clutch C4.

An eighth forward speed D8 is achieved by operating the fourth clutch C4and the fifth clutch C5.

A ninth forward speed D9 is achieved by operating the first clutch C1and the fourth clutch C4.

A reverse speed REV is achieved by operating the second clutch C2 andthe first brake B1.

In a state that the rotation speed of the input shaft IS is input to thefirst rotational member TM1 by operation of the first clutch C1 at thefirst, third, and ninth forward speeds, the second rotational member TM2is operated as the fixed element in the first planetary gear set PG1.Therefore, the first planetary gear set PG1 outputs a negative rotationspeed through the third rotational member TM3.

In a state that the rotation speed of the input shaft IS is input to thefourth rotational member TM4 by operation of the second clutch C2 at thefifth and seventh forward speeds and the reverse speed, the secondrotational member TM2 is operated as the fixed element in the secondplanetary gear set PG2. Therefore, the second planetary gear set PG2outputs a reduced rotation speed through the third rotation element TM3.

The compound planetary gear set CPG converts rotation speeds inputthrough the third rotational member TM3, the fifth rotational memberTM5, and the seventh rotational member TM7 and achieves the nine forwardspeeds and the one reverse speed.

The planetary gear train according to the first exemplary embodiment ofthe present invention combines four planetary gear sets with the sixfriction members such that the nine forward speeds and one reverse speedcan be achieved by operating the selected two friction members at eachshift-speed.

Since six friction members are used, a hydraulic control systemcontrolling the friction members can be simplified, and cost and weightmay be reduced. In addition, it is easy for the planetary gear train tobe mounted.

A sequential shifting is performed by releasing one friction member andoperating another friction member. Therefore, shift control may befacilitated.

In addition, speed ratio characteristic and a step ratio betweenneighboring shift-speeds at low gear ratio/high gear ratio demanded byvehicle power performance is almost uniform as shown in FIG. 3.

FIG. 4 is a schematic diagram of a planetary gear train according to thesecond exemplary embodiment of the present invention.

Referring to FIG. 4, the compound planetary gear set of Ravingneaux typeaccording to the second exemplary embodiment includes the long pinion P3having a large-diameter portion d1 and a small-diameter portion d2.

In addition, the large-diameter portion d1 of the long pinion P3 isengaged with the third sun gear S3, and the small-diameter portion d2 ofthe long pinion P3 is engaged with the common ring gear R34 and theshort pinion P4.

Therefore, arrangements and operations of the rotational members TM1-TM7and the friction members C1-C5 and B1 according to the second exemplaryembodiment are the same as those according to the first exemplaryembodiment except gear ratios. Therefore, detailed description of thesecond exemplary embodiment will be omitted.

FIG. 5 is a schematic diagram of a planetary gear train according to thethird exemplary embodiment of the present invention.

Referring to FIG. 5, the first and second exemplary embodiments use thecompound planetary gear set of Ravingneaux type, but the third exemplaryembodiment uses the compound planetary gear set including the third andfourth planetary gear sets PG3 and PG4 being single pinion planetarygear sets.

That is, the third planetary gear set PG3 is a single pinion planetarygear set and includes the third sun gear S3, the third ring gear R3, andthe third planet carrier PC3 rotatably supporting the third pinion P3engaged with the third sun gear S3 and the third ring gear R3.

The fourth planetary gear set PG4 is a single pinion planetary gear setand includes the fourth sun gear S4, the fourth ring gear R4, and thefourth planet carrier PC4 rotatably supporting the fourth pinion P4engaged with the fourth sun gear S4 and the fourth ring gear R4.

In addition, the third ring gear R3 is directly connected to the fourthplanet carrier PC4 and the third planet carrier PC3 is directlyconnected to the fourth ring gear R4.

Therefore, the planetary gear train according to the third exemplaryembodiment of the present invention includes seven rotational membersTM1-TM7.

The first rotational member TM1 includes the first sun gear S1 and isselectively connected to the input shaft IS so as to be operated as aselective input element.

The second rotational member TM2 includes the first planet carrier PC1and the second sun gear S2, and is directly connected to thetransmission housing H so as to be always operated as a fixed element.

The third rotational member TM3 includes the first ring gear R1, thesecond ring gear R2, and the third sun gear S3.

The fourth rotational member TM4 includes the second planet carrier PC2and is selectively connected to the input shaft IS so as to be operatedas a selective input element.

The fifth rotational member TM5 includes the third planet carrier PC3and the fourth ring gear R4, and is selectively connected to the inputshaft IS so as to be operated as a selective input element or isselectively connected to the transmission housing H so as to be operatedas a selective fixed element.

The sixth rotational member TM6 includes the third ring gear R3 and thefourth planet carrier PC4, and is directly connected to the output shaftOS so as to be operated as a final output element.

The seventh rotational member TM7 includes the fourth sun gear S4 and isselectively connected to the input shaft IS so as to be operated as aselective input element.

In addition, rotational members operated as selective input elementsamong the rotational members TM1-TM7 are selectively connected to theinput shaft IS through clutches C1, C2, C3, and C4, and the rotationalmembers among the rotational members TM1-TM7 are connected to each otherthrough a clutch C5.

In addition, the rotational member operated as the selective fixedelement among the rotational members TM1-TM7 is connected to thetransmission housing H through a brake B1.

The first clutch C1 is interposed between the input shaft IS and thefirst rotational member TM1 so as to operate the first rotational memberTM1 as the selective input element.

The second clutch C2 is interposed between the input shaft IS and thefourth rotational member TM4 so as to operate the fourth rotationalmember TM4 as the selective input element.

The third clutch C3 is interposed between the input shaft IS and theseventh rotational member TM7 so as to operate the seventh rotationalmember TM7 as the selective input element.

The fourth clutch C4 is interposed between the input shaft IS and thefifth rotational member TM5 so as to operate the fifth rotational memberTM5 as the selective input element.

The fifth clutch C5 is interposed between the second rotational memberTM2 and the fourth rotational member TM4 so as to cause the first andsecond planetary gear sets PG1 and PG2 to become direct-coupling states.At this time, the rotation elements of the first and second planetarygear sets PG1 and PG2 are operated as fixed elements.

The first brake B1 is interposed between the fifth rotational member TM5and the transmission housing H so as to operate the fifth rotationalmember TM5 as the selective fixed element.

In addition, the friction members according to the third exemplaryembodiment are operated at each shift-speed in the same manner as thoseaccording to the first exemplary embodiment are. Also, the thirdexemplary embodiment achieves the nine forward speeds and the onereverse speed. Therefore, detailed description of shifting processeswill be omitted.

The planetary gear train according to exemplary embodiments of thepresent invention combines four planetary gear sets with the sixfriction members such that the nine forward speeds and one reverse speedcan be achieved by operating the selected two friction members at eachshift-speed.

Since six friction members are used, a hydraulic control systemcontrolling the friction members can be simplified, and cost and weightmay be reduced. In addition, it is easy for the planetary gear train tobe mounted.

A sequential shifting is performed by releasing one friction member andoperating another friction member. Therefore, shift control may befacilitated.

In addition, speed ratio characteristic and a step ratio betweenneighboring shift-speeds at low gear ratio/high gear ratio demanded byvehicle power performance is almost uniform as shown in FIG. 3.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “outer”, “forwards” and “backwards”are used to describe features of the exemplary embodiments withreference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof. It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

What is claimed is:
 1. A planetary gear train of an automatictransmission for vehicles, comprising: an input shaft adapted to receiveengine torque; an output shaft adapted to output a shifted torque; afirst planetary gear set outputting a negative rotation speed by using arotation speed selectively input from the input shaft; a secondplanetary gear set outputting a reduced rotation speed by using therotation speed selectively input from the input shaft or to selectivelybecome a direct-coupling state together with the first planetary gearset; a compound planetary gear set having four rotation elements bycombining the third and fourth planetary gear sets, and changing therotation speed selectively input from the input shaft through two pathsand the negative rotation speed and the reduced rotation speed inputrespectively from the first and second planetary gear sets into nineforward speeds and one reverse speed and to output the nine forwardspeeds and the one reverse speed; seven rotational members including tworotation elements connected to each other or one rotation element amongthe rotation elements of the first and second planetary gear sets andthe compound planetary gear set; and six friction members includingclutches interposed between a selected rotational member among the sevenrotational members and the input shaft or between selected rotationalmembers, and brakes interposed between a selected rotational memberamong the seven rotational members and a transmission housing.
 2. Aplanetary gear train of an automatic transmission for vehicles achievingmultiple shift-speeds, the planetary gear train comprising: an inputshaft adapted to receive engine torque; an output shaft adapted tooutput a shifted torque; a first planetary gear set being a singlepinion planetary gear set having a first sun gear, a first planetcarrier, and a first ring gear; a second planetary gear set being adouble pinion planetary gear set having a second sun gear, a secondplanet carrier, and a second ring gear; a compound planetary gear set ofRavingneaux type having a third sun gear, a fourth sun gear, a commonplanet carrier, and a common ring gear; a first rotational memberincluding the first sun gear and selectively connected to the inputshaft; a second rotational member including the first planet carrier andthe second sun gear, and directly connected to a transmission housing; athird rotational member including the first ring gear, the second ringgear, and the third sun gear; a fourth rotational member including thesecond planet carrier and selectively connected to the input shaft; afifth rotational member including the common planet carrier, andselectively connected to the input shaft or to the transmission housing;a sixth rotational member including the common ring gear and directlyconnected to the output shaft; a seventh rotational member including thefourth sun gear and selectively connected to the input shaft; and sixfriction members including clutches interposed between a selectedrotational member among the seven rotational members and the input shaftor between selected rotational members, and brakes interposed between aselected rotational member among the rotational members and thetransmission housing.
 3. The planetary gear train of claim 2, whereinthe compound planetary gear set of Ravingneaux type includes the commonring gear, the common planet carrier, the third sun gear engaged with along pinion, and the fourth sun gear engaged with a short pinion engagedwith the long pinion, and the fourth sun gear is engaged to the shortpinion.
 4. The planetary gear train of claim 3, wherein the common ringgear is engaged to the long pinion.
 5. The planetary gear train of claim3, wherein the long pinion includes a large-diameter portion and asmall-diameter portion, the third sun gear is engaged to thelarge-diameter portion, and the common ring gear and the short pinionare engaged to the small-diameter portion.
 6. The planetary gear trainof claim 5, wherein the common ring gear is engaged to thesmall-diameter portion.
 7. The planetary gear train of claim 2, whereinthe six friction members include: a first clutch interposed between theinput shaft and the first rotational member; a second clutch interposedbetween the input shaft and the fourth rotational member; a third clutchinterposed between the input shaft and the seventh rotational member; afourth clutch interposed between the input shaft and the fifthrotational member; a fifth clutch interposed between the secondrotational member and the fourth rotational member; and a first brakeinterposed between the fifth rotational member and the transmissionhousing.
 8. The planetary gear train of claim 7, wherein the multipleshift-speeds include: a first forward speed achieved by operating thefirst clutch and the first brake; a second forward speed achieved byoperating the third clutch and the first brake; a third forward speedachieved by operating the first clutch and the third clutch; a fourthforward speed achieved by operating the third clutch and the fifthclutch; a fifth forward speed achieved by operating the second clutchand the third clutch; a sixth forward speed achieved by operating thethird clutch and the fourth clutch; a seventh forward speed achieved byoperating the second clutch and the fourth clutch; an eighth forwardspeed achieved by operating the fourth clutch and the fifth clutch; aninth forward speed achieved by operating the first clutch and thefourth clutch; and a reverse speed achieved by operating the secondclutch and the first brake.
 9. A planetary gear train of an automatictransmission for vehicles achieving multiple shift-speeds, the planetarygear train comprising: an input shaft adapted to receive engine torque;an output shaft adapted to output a shifted torque; a first planetarygear set having a first sun gear, a first planet carrier, and a firstring gear; a second planetary gear set having a second sun gear, asecond planet carrier, and a second ring gear; a compound planetary gearset formed by combining a third planetary gear set having a third sungear, a third planet carrier, and a third ring gear and a fourthplanetary gear set having a fourth sun gear, a fourth planet carrier,and a fourth ring gear; a first rotational member including the firstsun gear and selectively connected to the input shaft; a secondrotational member including the first planet carrier and the second sungear, and directly connected to a transmission housing; a thirdrotational member including the first ring gear, the second ring gear,and the third sun gear; a fourth rotational member including the secondplanet carrier and selectively connected to the input shaft; a fifthrotational member including the third planet carrier and the fourth ringgear, and selectively connected to the input shaft or to thetransmission housing; a sixth rotational member including the third ringgear and the fourth planet carrier, and directly connected to the outputshaft; a seventh rotational member including the fourth sun gear andselectively connected to the input shaft; and six friction membersincluding clutches interposed between a selected rotational member amongthe seven rotational members and the input shaft or between selectedrotational members, and brakes interposed between a selected rotationalmember among the seven rotational members and the transmission housing.10. The planetary gear train of claim 9, wherein the first planetarygear set is a single pinion planetary gear set, the second planetarygear set is a double pinion planetary gear set, the third planetary gearset is a single pinion planetary gear set, and the fourth planetary gearset is a single pinion planetary gear set.
 11. The planetary gear trainof claim 9, wherein the six friction members include: a first clutchinterposed between the input shaft and the first rotational member; asecond clutch interposed between the input shaft and the fourthrotational member; a third clutch interposed between the input shaft andthe seventh rotational member; a fourth clutch interposed between theinput shaft and the fifth rotational member; a fifth clutch interposedbetween the second rotational member and the fourth rotational member;and a first brake interposed between the fifth rotational member and thetransmission housing.
 12. The planetary gear train of claim 11, whereinthe multiple shift-speeds include: a first forward speed achieved byoperating the first clutch and the first brake; a second forward speedachieved by operating the third clutch and the first brake; a thirdforward speed achieved by operating the first clutch and the thirdclutch; a fourth forward speed achieved by operating the third clutchand the fifth clutch; a fifth forward speed achieved by operating thesecond clutch and the third clutch; a sixth forward speed achieved byoperating the third clutch and the fourth clutch; a seventh forwardspeed achieved by operating the second clutch and the fourth clutch; aneighth forward speed achieved by operating the fourth clutch and thefifth clutch; a ninth forward speed achieved by operating the firstclutch and the fourth clutch; and a reverse speed achieved by operatingthe second clutch and the first brake.